Means for equalizing transmission over lines of different electrical characteristics



June 19,1923.

. 1,459,003 I K THOMPSON G. MEANS EOfi EQUNLXZING TRANSMISSION OVER LINES OF DIFFERENT ELECTRICAL 1 H CHARACTERISTICS Filed Oct. 29 1918 3 Sheets- Sheet 1 [III/II II.

4 MUZZZZEEW ATTORNEY June 19, '1923.

G. K. THOMPSON MEANS FOR EQUALIZING TRANSMISSION OVER LINES QF DIFFERENT ELECTRICAL CHARACTERISTICS Filed Oct. 29 1918 3 Sheets-Sheet 2 INVENTOR. (Z if Thompson /ggf A TTORNEY June 19, 1923.

1,459,003 G; K. THOMPSON MEANS FOR EQUALIZING TRANSMISSION OVER LINES OF DIFFERENT ELECTRICAL CHARACTERISTICS Filed Oct. 29, 1918 s Shets-She't 5 INVENTOR. E Ikampsm A TTORNE Y Patented June 19, 192a.

MEANS FOR EQUALIZiNC 'rnimsivilssron oven; LINES or CHARACTERISTICS;

- I I a i a N we ariessl eao Amman PHONE 'ANDTEILEGRAPH COMPANY, A CORPORATION or NEW'YORK. a

Application filed O ctober29, 1918. Serial No. 260,147.

To allwhomitmayconcemq Be it known that I, GEORGE K; TrroMrso residing atv Maplewood, in the county of Essex and State of New Jersey have in vented certain Improvements in Means for Equalizing Transmission Over Lines of Different Electrical Characteristies, of which the roaming is a specification This invention relates to telephone systerns and more particularly to the provision of means whereby the transmission over telephone, lines of di fierent electrical" char act eristics ma be equalized o r re nde red more uniform. g H a by Telephone l nes have, ln general, difierent electrical characteristics varying with the length of the lines. F or any particular typev ofline construotion which may be employed the resistance, eap'acity, inductance and leak- .age of the circuit increase with the lengthj scribe jhaving a long line, 'Vwhen connected,

with any other subscriber, does not receive as good telephone transmission as would a subscriber having a short line similarly connected, Furthermore, in the common battery systems now so generally employed all but small communities, the'resistance of the line causes a further efi'e ct on the transmission in that it' reduces the amount of direct current which the transmitter re- Ceives from the central oflice battery and so rendersit less efiicient in the generation of the alternating telephone C urrent.

v In viewof the onditions above referred to, it has not been heretofore possible to,

provide all subscribers with thesarne grade oftransmission and it is one of the fobjects of thisinvention to provide means whereby this difficulty may .be overcome, although nrrrn'nnitr answerer other and objectsiotlthe;

after, given.

will appear from the description herein- The objects characteristics of the line. I Where thegtfans of this invention ymay base: a cured by associating with each ,line, av telephone transmitter jwh'ose resistance adjusted accordanoe withfthe electrical 1 160 mission line is lof high impedanee,;,;since he irec cu ren supp ie ath tr n mit; a ter over; the line is small, the transmitter,

9 1 .d-b ,Q high r ist nce/settl fq'raa s eniver no h fi a smit err stane .p fi e at a eria qnrd iheal re i tanc inclu ingat atr the; l n be procl11eed,' and consequentlya greater a transmission efliciency will result, ,Where rent supplied vlarge, the transmitter resist- We ehduld e. mr at elyasma l it 'at a given ariation in the transmitter resista-nee ,produces a 'relatiyelyg small variation a in, the total: resistance, Consequently the" transmission efficiency under this ,cbnditimij e ,l is, of 9W p dan .rei kt elc i z may be made little ifanyzgreater than under i the first condition above mentioned T ell' i ma sec d in, aeo di anoe the; present invention i provid ing a transmitter having a plurality of Iva-tie.

may be conneotedlin a plurality (of.,dif l'efrentl .relatiohsto produce; a transmitternhavin g on the character. of the li ne .with whioh, it is to be associated. SinceinQpraetice it is. not expedient to providela 'sullioientjnumberl of paths for th 'transmitter to give" a .siifg differenteffective resistances depending up- -fieiently large number ofeffeotivezresist a nces to correctly; adapt the transmitter to, l nesof any-impedance, the invention 0on templates grouping the lines aecordingto' their impedance and providing'jeach line 111 17116 group w th ,a tran'smitter whose re-I' sist'ancef is adjustedin accordance with the average impedance of'the'lines. ofthegroup Preferably the multiple paths'through .the',

transmitter may be secured by providing'f the transmitter with a granular "carbonere; sistance button, the electrodesfof. which; are

of sections, adapted divided into i a plurality to be variably interconnects The invention may-nowbenfully 1'. I

"showing several ways of interconnecting the sections of the electrodes of the transmitter in Figure 5;

Figures 9'to 18 inclusive are views illustrating various detalls of the transmitter of "Figure '5.

Referring to Figure 1 a telephone transmitter is shown comprising the usual front casing 1, back casing'or shell 2, mouthpiece 3, supporting bridge 4 and diaphragm 5. Suitably mounted upon the supporting bridge 4'and electrically insulated therefrom is a granular carbon resistance button 6 comprising a back electrode 7 and a front electrode 8, between which is placed a suitable amount of granulated carbon, said front electrode 8 being carried by and movable withthe diaphragm 5. The front electrode 8 as shown'in Fig.2 comprises two sections 9 and 10 separated by an insulating member 11. The sections 9 and 10 are electrically connected to binding posts 12 and I 13 mounted upon the supporting bridge 4 and insulated therefrom. The back electrode 7 is electrically connected through the body of the, resistance button 6 to a binding screw 14 which is also insulated from the supporting bridge 4. It will be seen thatby means of this arrangement two variable resistance paths extend through the button 6, one from section ,9 to back electrode 7 and the other from section 10 to back electrode '7. A third path extends between sections 9 and 10 which is of relatively'high resistance. This path is through the granular carbon alone.

Referring now to Figure 3 which shows the circuit connections of the transmitter of Figurel as applied to a line of high impedance, the line L is connected at the central station to a common source of battery supply current B while at the subscribers station it terminates in the usual subscribers set including receiver R, transmitter 6, induction coil 14, ringer 15 and condenser 16. From the terminal 17 of the line a connection extends to binding post 13, section 10 of the front'electrode, through the granular carbon to back electrode 7, thence through the granular carbon 'to section 9 of the front electrode, thence to binding post 12 and through one winding of the induction coil 14 to the terminal 18 of the line. It will be noted that the circuit above traced includes two paths through the resistance button 6 in series, so that the resistance of the transmitter is relatively high, thereby producing a high power transmitter suitable for use in connection with lines of high impedance suchas the line L. The direct'path between sections 9 and 10 is neglected since it is of relatively high resistance compared with the above paths. 4

Where the transmitter is to be used in connection with a line of'low impedance such as the line L of Figure 4, the binding posts 12 and 13 are strapped together and a circuit extends from terminal 17 of the line to the'binding screw 4, and the back electrode 7 of'the resistance button 6 and thence in parallel through the granular carbon resistance to the sections 9 and 10 of thefront electrode, from which point the circuit continues in parallel to the binding posts 12 and 13, wherethe two paths merge and the circuit continues through one winding of the induction coil 14 to the'terminal 18 of the line. It will be seen that in this case the'two paths through the resistance button'tl are connected in parallel, thereby'materiallyfreducing the ell'ective resistance of the transmitter so that when associated with a low impedance line such as the line L itsf ciency will be lower and the resultant trans mission will be comparable to that secured when the transmitter is connected as shown in Figure 8 to a line'of high impedance. 7

l'nFigure 5 a inodified form of transmitterwis illustrated, the resistancebutton 6 in" this case including a front electrode 19 :and back electrodeQO, each electrode comprising two sections of different area, the structure I being shown more clearly in Figures 9 to 18L As shown in Figure 14 the front electrode is mounted upon the mica diaphragm 21 and annular secis secured to I is secured to the dia ')liragm 5 bv means of the screw connection 26. The front electrode support 24 is provided with an M11111;

lar )ro'ection 27 extendin between the inner and outer sections of the front electrode 7 in order to insulate the sections from each other. The back electrode 20 is likewise composed of two sections, one being an inner circular section 28 and the other ani outer annular section 29. lar section is mounted uponthe body 30 of the resistance button 6, while the inner sec The outer annuif ti0n28 is mounted on the back electrode in sulator 31 and is provided with a stud 32 and a nut'33 insulated from thebody 30 for completing electrical connections. to the inner section. The back electrode vinsulator 31 is seated in an opening through the body 30-and is provided with an annular projection 3e for the purpose of insulating the outer andv inner sections of the back elec-,

trode. It will be seen that by means of this construction'the inner and outer sections of each of the electrodes are electrically insulated from each other;v I i Returning now to Figurefi the outer secinsulated therefrom.- The inner section 22 ofthe' front electrode is electrically connectedto the diaphragm 5 by means of the screwconnection 26 already referredtoQ The diaphragm= 5 is connected by meansiot conductor37 with the binding post 38 mounted uponthe supportingbridge 4 in a manner similar to that described in connection with the binding post 36. The outer section of the back electrode is an'electrical connection with the body 30 of the resistance button 6 which is connected to a binding screw 39 insulated from the supporting bridge 4, the body of the resistance button; 6 being likewise'insulated from the supporting" bridge 4 upon which it is mounted; The inner section 28 is insulated from the body 30 as al-- ready stated by the back electrode insulator 31 and connections may be made to the inner section 28 by means of the nut 33.

theirseveral terminals as above described furnish a convenient means whereby the transmitter may be connected in a number of different ways in order that itimay have Where the;

different effective resistances. transmitter is to be associated withaline of highimpedance, one line terminal may be connected to the bindingpost 33 asshown in Figure 6, and the other line. terminal to the binding post 38 so. that the connection through the resistance cups-only includesthe inner sections 22 and 28 of the front and back electrode which are of relatively. small area, so that the transmitter'will now be a high reslstance transmitter, Where the transmitter is to be associated with a line of medium impedance the connectionsshown in Figure 7 may be employed. Inthis figure one terminal of the line is connected to the-binding screw 39 and ,theother terminal to the binding post 36, so that the resistance path through the transmitter includes only defined ingthe appended claims:

provided; Where the transmitter is to "be associated witha line of low impedance the bindinig'p'ost .33 and the binding posts '36 and138 will also be strapped together as shown in Figure 8. One line terminal 'Inay binding screw 39 will be strapped to'the then be connectedito thebinding'screw 39 1 and thefother line terminalto'thebinding post36, so that the two sections ofeach electrode are connected in parallel and two par-- allel resistance paths are completedwith the resistance buttons. Bymeans of this connec tion a transmitter of low resistance is pro videda The transmission lines may be grouped in accordance with their impedancesf into three groups and the three different:

forms of connections may be" employed' for" '1 the'transm'itters associated with the three -1 group's. I

Itiwill be 'seen'that'by means of the arrangements above described a simple though" efficient means has-been provided whereby the 'telephonictransmission over lines of 'dif I ferent chara'cter'may be equalized andren dere dmore un-iform, so that subscribers.hav-' in'g instruments "onloops of different length will received-substantially the same transv in ssion. It' will alsodbeobvious that the, general principles herein disclosed may be I embodied in many. otherorg'aniz ations widely different from those illustrated without.- departing from the Sp' it of the What is claimed'is: 1. A telephone transmitter for use in connection with lines of different electrical characteristics, said'transmitter including a I single variable resistance button coinprisirlg, I The sections of the two electrodes with a casing'having a unitary mass of granu r lar material therein and also having opposed, electrodes movable with'respect' to each other, one of said electrodes 'compris-i ing a plurality of sections, anda plurality I. I v

ofterminals for interconnecting said electrodes! differently to form. a plurality of cordance ,with' the electrical characteristics of theline with which the transmitter is to V be used, a l f 2. A telephone transmitter-for usein conpaths throughsaid granular materialin acr15, 'nectionwith lines of different electrical J Y characteristics, said transmitter including a single variable resistance button comprising I 1 acasing having a unitary mass'of granular mater al therein and "also having opposed electrodes movable with respecttto each other, each 20f. said ele'ctrodeshcomprising a v invention as nection with lines 01": difierent electrical characteristics, said transmitter including a single variable resistance button comprising a ising having a unitary mass of granular material therein and also having opposed electrodes'niovable with respect to each' other, each oi? said electrodes including a plurality oi 'sections of difi'erent area, and a plurality of terminals for interconnecting said sections diti'erently to form a plurality of paths through said granular material in accordance with the electrical. characteristics of the line with which the transmitter is to be used.

4. A telephone transn'iitter for use in connection with lines of diiferent electrical characteristics, said transmitter including a single variable resistance button comprising a casing having a unitary mass of granular material therein and also having opposed electrodes movable with respect to each other, each electrode comprising a plurality oi? sections of different area and a plurality of terminals for completing a variable resistance path through the granular material of said buttonlying between sections of small area of the two, electrodes, or lying between sections o'l' large area of the two electrodes, .-or lyre between'a' plurality of set-tons oi. the two electrodes connected 1n o used.

a. A tcleghone transmitter for use in connection w n lines of different electrical T. Ciltll'ZlCLQl therein and also having a plurality of elec trodes separated by granular materiahand Jeans for rarying the effecti e conductingname to this specification this 19th day of GEORGE K. THOMPSON.

ccurding to the electrical charac- L the line with which the transmitics said transmitter including a single resistance button comprising a casing having a unitary mass 0t granular material I 

